Many heat shrinkable polymeric films are known which can be heat shrunk around a reusable closure attached to an outlet portion of a container to provide a seal that assures a subsequent user that the contents of the container have not been tampered with. U.S. Pat. Nos. 2,790,286, 4,014,734, and 4,000,824 show known examples. While such seals can be effective, the materials described for use as such seals are either not easily torn along a predetermined straight line, require inclusion of a tear strip or need to be perforated to produce a straight line tear, are not sufficiently heat shrinkable to closely conform to the outer contours of a closure and container, and/or are relatively expensive for use as seals.
Known uniaxially oriented polyolefin film materials are generally not suitable for such seals because they are either inadequately processed to provide sufficient heat shrinkability and controlled tearing, or are oriented to such an extent that the film material fibrillates (e.g., U.S. Pat. Nos. 3,491,419 and 3,739,053).